What’s your favorite industry event? It’s a simple question, but it’s a game changer for event marketers. If your attendees aren’t telling their friends and colleagues about your event, you won’t see the new, qualified attendees who are the lifeblood of your event.

Why would someone take the time and stake her relationship collateral to recommend a conference or a tradeshow to a friend, a client, or a colleague? In my firm’s analysis, covering millions of attendees on multiple continents and across almost every industry, we’ve discovered that there are four motives in play. If you understand them, you understand how to get your participants to bring that crucial contact who does not know of your event or is on the fence about this year.

1. Connections

The biggest motivator for people to advocate for your event is the desire to connect with the members of your community they know and should know. They want to grab a drink, meet for coffee, discuss a deal, share a new idea, etc. This is particularly true for highly valuable networking events, likeWeb Summit, AdTech and Davos. The best thing you can do for them is make it easy to search and explore other members of the community.

2. Passion for your brand

Next, people sincerely want to advocate because they love your event and want others to love it also. This can be an even larger portion for events where the community is more passionate. Think ComiCon and Money 2020, for example. The best thing to do for them is to make it easy to word-of-mouth market your event to their network

3. Personal Brand

Another 20% of the time people are moved by wanting to see and be seen, especially as a leader, as someone of influence. They want to show off that they are going. This is particularly true for powerful brands such as CES, SXSW, and the Cannes Film Festival. The best thing to do for them is to help them show off their leadership and influence within the community.

4. Incentives

Lastly, 12% of the time advocates are motivated by material incentives. The best thing here is to offer your top advocacy leaders a prize that is relevant to the community. For example drones for top advocates at the Drone Expo, or VIP passes for Coachella.

You may be surprised that material incentives are not the biggest motivator. Word of Mouth marketing is so effective because it is based on trust, and cannot be purchased. Largely this is because the most influential people, with the largest networks, know the value of their network. What they want–and what you can use to motivate them–is a large event community from which they want recognition and respect. Once you fully engage that community they will do your work for you.

Michael Barnett is CEO of InGo. Opinions are his own. He can be reached at mike@letsingo.com.